234 
Lead 
above circumstance ; and should any of your readers be 
able and willing to give me any further particulars re- 
specting this manufacture, which may be conducive to 
the health of those employed in it, they will much oblige 
A CONSTANT READER. 
Mr. John Brierlet/s ( Greenfield. Flintshire J Latent for 
a new mode ofi setting Blue Lead for corroding the 
same into White Lead . 
THIS method, by means of a bed of dung or bark ? 
into which are inserted pots filled with acid ; over these 
are placed boards having holes bored in them to admit the 
vapour of the acid round the rolls of lead. On these ano- 
ther bed of dung or bark is placed, and the process re- 
peated before, forms a second bed ; these beds may be 
repeated to any practicable extent, and are denominated 
a stack. There is a chimney or fine running through all 
the beds, for the purpose of distributing the vapour of 
the acid equally through them all, for which purpose that 
part of the flue, which extends from the one bed of dung 
or bark to the other, is left with small interstices between 
the bricks, so as to communicate any superfluous vapours 
above or below, or carry off to the other bed any vapour 
which may be to spare in that bed. 
The observations of the patentee refer 1. To the num- 
ber of pots, and the difference as to the expense of them. 
2. To the health of the manufacturers. 3. To expenses 
of the annual breakage. 
With respect to the 1st. According to the above plan 
a bed may be set with 280 pots of equal effect with a bed, 
which, according to the old mode, would require 560 
pots, making a difference of one half. The pots used in 
the plan cost 2d. each ; those in the old method 5d. each. 
§o that 280 pots at 2d. each will cost 21. 6s. 8d. and 560 
pots at 5d. will cost llh 13s* 4d. leaving a difference in 
